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ENDURO S— Chromium 13%, carbon under .12%. Suit- 
able for applications where moderate corrosion resistance 
combined with high strength and toughness are required. 
Oxidation resistance to 1500° F. 

ENDURO FC— Similar to "S" but with free machining 
qualities added. 

ENDURO AA— Chromium 17%, carbon under .10%. For 
applications where corrosion resistance is more important 
than high strength or toughness. Good bending and form- 
ing qualities. Oxidation resistance to 1600° F. 

ENDURO KA2— Chromium 18%, nickel 8%, carbon under 
.16%. Excellent general corrosion resistance to atmos- 
•here, salt air, food and dairy products, nitric acid, etc. 
High ductility and best drawing qualities. Oxidation resis- 
tance to 1600° F. 

ENDURO KA2S— Similar i KA2," but with carbon under 
.07%. For applications requiring high physical properties 
above 1000° F. and for welded fabrication where subsequent 
heat treatment is not possible. 

ENDURO KA2B— Similar to "KA2/' but with added sili- 
con. Oxidation resistance to 1700° F. 

ENDURO KA2Mo— Similar to "KA2" but with 3% mo- 
lybdenum added. 

ENDURO HC— Ch mum 28%, carbon under .20%. De- 
igi 1 for oxidation ance to 2100° F., where great 

•ngth and toughness are not required. High resistance 
to sulphur and sulphur ga^es, hot or cold. 

I NDURO HCN— Chromium 23%, nickel 12%, carbon 
i !er .20%. Oxidation resistance to 2100° F., \ h physical 
] gher than "KA2S." 

ENDURO KNC-3— Chromium 25%, nickel 217c, carbon 
under .25%. For applications requiring highest strength and 
nidation resistance at highest temperatures. 

are produced undtr Krup] a patents. 






OST present or prospective users 

of stainless alloys have at some 
time been conscious of a lack of accurate basi< 
information which would permit them to select 
intelligently and to fabricate successfully the par- 
ticular type of stainless best suited to a »i\en re- 
quirement. Obviously, no single type can meet all 
conditions of corrosion and temperature. A series of 
booklets has therefore been prepared to supply thi 
e\;iet information on the Enduro Stainless Irons. 

Stainless Iron generally is an allo\ of iron and 
chromium, or of iron, chromium and nickel, with 
ver\ low carbon content. The stainless properties 
of the alloy are due to the ability of chromium to 
form with iron a solid solution which is resistant 
to the various corrosi\e media. It is essential that 
sufficient chromium be present in solid solution t<. 
ensure stainless properties. The chromium con- 







tents of Enduro Stainless Irons have been adjusted 
accordingly , 

Stainless irons as a class do n<>l respond to hard- 
ening 1»\ heal treatment. Neither do the} require 
special heal lieatment other than thai received al 
the mill to develop stainless properties. Stainless 
irons a- a class lend themselves to deep drawing and 
other forming operations. 

There is a distinction between stainless iron and 
stainless steel, though the latter term is popularly 
if erroneously used lo desj^nale all stainless alloys 
StrietU speaking stainless steel is an alloj of iron, 
chromium and carbon. The amounl of carbon i 
Mich that the material harden* upon quenching. 
This branch of the stainless family is suitable for 
cutlery and applications where high physical prop- 
erties, hardness and wear resistance are required, 
but does not lend itself to deep drawing or forming. 

Not only does stainless steel require very careful Selection of Type and Finish — Enduro 

polishing, but it must also be carefully heat treated 
before polishing to develop its corrosion-resisting 

Types of Enduro Stainless — To meet the de- 
mands of industry for corrosion- resisting alloys 
suitable for a wide variety of specific purposes, the 
Enduro Stainless Irons have been developed in a 
number of types. In this development all factor- 
ail ting corrosion resistance have been considered 
nd their relative importance established. The 
esult is a series of alloys possessing maximum 
corrosion resistance and physical properties, con- 
sistent with ease of workability, for each field of 
ipplication. ll is noteworthy that this has been 
accomplished without undul) increasing the cosl 
of I he alloys. 

Stainless Irons are furnished in several different 
finishes. The finish of the stock used will depend 
on the amount of forming necessary. Jt is inadvis- 
able to use polished sheets for extra deep drawing 
operations where score marks from dies are likeh 
to occur in forming or where it is necessary l<. re- 
anneal to make a second drawing operation. An 
unpolished, fully annealed and pickled sheet 
designated as our number one (1) finish should be 
used. Polished finish should he used onl\ where 
stock will be employed without further working 

or where the degree of working is small. 

Corrosion Resistance 

Much harm has been 

done by exaggerated claims of corrosion resistance. 

Metals and alloys are resistant to corrosion in 


erent degree, none being entirely proof against 

all corrosive agent-. Each melal or allo\ is limited 

as to the field in which ii is serviceably resistant; 

hence while it may possess excellent resistance in 
its field, it by no means follows that it will be 
equally resistant to all attacking media under all 

To simplify this problem we group the application 
of l he Enduro Stainless Irons under three headings: 

1 . Atmospheric Corrosion — understood t«» 
mean exposure to weather conditions. 

2. Wet Corrosion — understood to mean 
partial or total immersion in corrosive 

:5 . Dr\ Corrosion — understood to mean seal- 
ing at elevated temperatures. 

Atmospheric Corrosion — In this field the 

Enduro Stainless Irons are excelled by no other 
stainless alloys. The higher the allo\ content of 
each Enduro type, the more resistant I he alloy is 
to corrosion by weather exposure. In addition to 
this result from higher content of alloys, the form- 
ing and deep drawing qualities also are favorabh 
influenced, particularly b> the addition of nickel. 
Ml types of Enduro Stainless Irons produced b\ 
Republic Steel Corporation are suitable for general 
resistance to atmospheric corrosion. 

Wet Corrosion — Enduro Stainless Irons are 
resistant to nitric acid and similar oxidizing agents. 
to sulphur and sulphur compounds and to the more 
common organic acids occurring in the household. 
They are not resistant to hydrochloric or sulphuric 
acids except under special conditions. 

The rate at which corrosion (solution of the allo> 
in the corrosive liquid) takes place depends upon 
a number of factors, among which are the con- 
centration of the other elements in the solution and 
the character of the solvent; the temperature; the 

^late of the solution, whether agitated or at rest; 
the amount of dissolved oxygen or other oxidizing 
agents present; the presence of impurities in the 
solution which might act as inhibitors, or them- 
selves attack; electrolytic action because of contact 
with other metals, etc. 

Since these and other factors affect the rate at 
which corrosion takes place, it is questionable 
whether laboratory tests on the stainless irons are 
of great practical value except insofar as the> in- 
dicate whether attack does or does not take place 
and if it does, whether rapidly or slowly. Tests on 
samples of Knduro Stainless Irons under actual 
conditions are much preferable to calculations of 
probable corrosion rate based on laboratory data. 
The Republic Steel Corporation has a large amount 

of corrosion data obtained from bests in pun 
solutions and also from actual application of Ih 
various alloys under service conditions. If the pro- 
spective user of Enduro Stainless will submit the 

application to our metallurgical department a 

recommendation will be made. 

Dry Corrosion — Enduro Stainless Irons are 

resistant to scaling at elevated temperatures. Each 
type is best suited for certain conditions and tem- 
peratures. All Enduro Stainless [rons are resistant 
to sulphur gases up to 1000°F. 

In dealing with the application of Knduro Stainless 
Irons to high temperature service it is important 
to differentiate between intermittent and contin- 
uous service. This is necessary because >me of the 
stainless alloys have a tendency to cast ofF their 

protective scale when alternately healed and cooled. 

due to difference in the coefficient of expansion 
between the scale and the metal itself. There ha> 
been established a maximum temperature foi 
these service conditions which is given for each 
t \ pe of nduro. 

Physical Properties at High Temperatures 

\ selecting a material for the 

design of equipment which is to 

be used under high temperature conditions, where 

high stresses ma\ he encountered, as in oil refiners 
operations, the following qualifications are neces- 

ar\ : 

(;«) The metal must have tin* requisite strength at the 
sprrilh'd lemperal ure. 

(\>) l\ must not oxidize under ihe action of tin- Name or 
hot gases. 

(c) 1 1 iim-i noi heroine brittle while in service. 

(d) It must n isl Lhe corrosive action of the materials with 

v\ hich it is in conl u I -urh us liquids, pases, etc 

Enduro on th« Chryvl«r Tc 

I ' I e 1 1 * t r e r \i I m- i a r i I \ d « 

MM! | r li 'lli| || K*s Ih.l L| 

.1 illy * il h the rati tt w hi* h in plied. 

But when the test is made at high temperatures 

the rate of pulling of the tensile lest piece has a 
marked effect on the ultimate tensile strength 
obtained. The more slowly t lie test piece is pulled, 
the lower is the strength shown by it- It is thus 
apparent that the tensile strengths of metals at high 

temperatures as ordinarily determined by short-lime 
tests cannot be used tor design purposes. It is 
equally evident that the effect of stress on the metal 
held ai a high temperature for a long time must he 
known before it is possible intelligently to design 

equipment to be used under- such conditions. 

I f the strength of a meial at a given high temper- 
ature is determined onl> b> ordinary tensile tests. 

piece of equipment subjected to that temperature 
lor i longer time, under pressure, using a safe liber 

Lress as determined l>> ihe short-time tests, will 
pr< -i\el\ stretch, or "creep." This will con- 
tinue until a point is reached where the metal 
thickness becomes so greath reduced thai the 
pressure can no longer be withstood, and the ap- 
paratus will fail. 

li is well to note thai this reduction in the thickness 
of the metal ma> also be hastened b> the effects of 
rrosion n of oxidation, or a combination of both 

In order to design apparal us or equipment suitable 
for service at various H«-\ aicd temperatures, when 
stn i - will be high, il is necessary to determine the 
• reep strength* 1 of the metal. The "creep strength" 
i a given temperature ma) therefore be defined 
as ih« tress .ii which the metal will elongate r, 
during 1 00, 00 n or lu.noo I - ad that temperature 

The n ep strength* 4 of ea<-h Knduro type, 

mpared to plain carbon steel in given in com 
pai m undei i h i ype. In applying this data i 

problems of practical design Jes should be | <| 

correspond ii to the highest temperatures an- 

i ieipated i i fai o»r of -;dei \ iDtrodu< ed to prevent 
d- 4 1 s being em ceded, should the temperature 

l< ri I all \ be in 



A Few of the Polishing Machines in Republic's Finishing Division 

Preparation of Surface Polishing 

HE preparation of the surface to 
be exposed to corrosive attack is 
of the utmost importance. When the highest degree 
of corrosion resistance is desired, the scale resulting 
from hot working must be removed and the surface 
ground and polished. 

To secure the permanent, beautiful, silver-white 
lustre characteristic of Enduro Stainless Irons, 
which permits them io replace such materials as 
nickel plate, chromium plate, nickel silver, tinned 
copper, and the copper nickel alloys, it is necessary 
that certain precautions be observed. Polishing 
and buffing equipment which has been used for 
polishing other metals should have all such metal 

particles carefully removed before use in polishing 
Enduro. Careful selection of polishing grits and 
buffing compounds is necessary to insure their 
freedom from iron, as otherwise such iron ma> be 
worked into or remain on the surface of the polished 
article and will under corrosive conditions give the 

erroneous impression thai the stainless alloy i^ 

V factor of equal importance is that all surface 
imperfections must be removed to secure maximum 
corrosion resistance. In polishing flat surfaces it 
is necessary to begin operations with coarser grits 
than when polishing formed articles. The rule 
should be to use the finest abrasive possible and 


yel remove all of the surface imperfections, the 

that coarse grit marks are verv 

than (hat of polishing, 7200 to 12000 lineal feet per 



difficult to remove. 

A polishing speed of from 5000 to 7000 lineal feet 
per minute is productive of very good results. The 
first few polishing operations may be done dr> . but 
the final operation should be done on greased 
wheels. Care must be exercised not to burn the 
work, the lower coefficient of thermal conductivity 
making this danger greater than when polishing 
copper, brass or steel. 

The bulling of Enduro Stainless Irons must be done 
with iron-free bufling compound. This precludes 
the use of ordinary jeweler's rouge. Green chrome 
oxide is a suitable material where a mirror finish 
is not necessary; however, when such a finish i- 
necessary special buffing ((impounds are required 
followed by the use of chromium oxide to bring out 
the color. The speed of bufling should be higher 


As regards polishing, the character of the finish of 
the exposed surface is the most important factor 
in producing resistance to stain and tarnishing; 
hence, the more perfect the finish, the less the like- 
lihood that the metal will slain. 

When formed articles do not require maximum 
resistance to corrosion and are to be used in I lie 
"as drawn" or semi-polished condition, it is recom- 
mended that the article be given a passivation or 
cleansing treatment. 

When using stainless iron in the semi-polished con- 
dition there will usualW be some 4 discoloration of 
the exposed surface. This eventually develops 
into a permanent, tightly adherent surface coating 
which, if appearance is not a primary consideration? 
does not adversely affect the life of the metal. 

Passivation of Enduro Stainless Alloys 

Polished sheets as furnished for exposure to weather 
conditions are given a special surface treatment 
before shipment from Republic Steel Corporation, 
This treatment is known as a "Passivation Treat- 

ment and insures proper resistance to corrosion, 
staining, and discoloration. 

In installing such polished sheets on buildings the 
fabricator will often find it necessary to cut, 
machine, punch, shear, bend, or otherw ise work the 
metal with the result that the passivated condition 
is destroyed. In forming the sheet the forming tools 

It impossible to immerse pieces, all sheared edge 
drilled or punched holes, engraved or scratched 
surfaces should be swabbed or scrubbed with the 
above nitric acid solution. 

3. Rinse in clear water to remove all traces of 
acid, and dry. 

usually are made of regular die steel. There is a 
possible abrading action between the stainless metal 
and the steel die which may leave a surface film of 
iron on the stainless surface after the forming opera- 
tion. This film should be removed by the passivating 
treatment as otherwise a form of rusting wi 
appear after the unit is placed in service. With 
certain forming operations it is possible to use 
paper or other lubricating compounds between 
the stainless metal and the steel die, which will 
prevent the abrading action. 

Cleaning of Polished Enduro— To keep 

polished Enduro surfaces clean, use soap and water, 
with a 4 'grease free" drying and polishing cloth. 
\\ here necessary to use a polish, Bon Ami is recom- 
mended. Do not use liquid metal cleaners, as they 
are liable to dull the lustre. 

Tile and brick cleaning compounds are likely l<» 
contain ingredients which may etch or discolor 
Enduro Stainless and il is therefore recommended 
that when Enduro is installed in conjunction with 


(ile or brick it be wiped with a greasy cloth to 
protect the surface when the lile is cleaned. 

Use o 


Contact with Other Metals — The 

polished Enduro Stainless sheet and trim on I be 
Where this is not possible it is recommended that outside of buildings may necessitate the use of 

after such operations the metal surface be repas- steel supports that are welded or otherwise attached 

to the stainless metal and then attached to the steel 
structure of the building. These points of contact 
of steel to stainless should be protected from cor- 
rosion as much as possible; a coating of paint is 

sivated in I lie following manner; 

1. Wash thoroughly in kerosene to remove all 
traces of grease, drawing compounds, etc, and 
dry by rubbing with whiting. 

2. Immerse in a 20% by volume solution of 
commercial nitric acid at a temperature of 130°F. 
for 20 to 30 minutes. This acid will not attack 
ihe metal nor destroy the surface finish. (Tanks 
for holding such acids should be lined with stain- 
less alloy.) 

The contact of Enduro Stainless with other metal 
should be avoided where electrolytic corrosion i- 
apt to occur (wet corrosion). Under all other condi- 
tions, it is satisfactory to have Enduro Stainless in 

contact with dissimilar metals. 


Following are a few of the applications in which the various types of Knduro have met 

with conspicuous success. 

Enduro K A 2 

Bottling machinery. 

Canning and preserving equipment. 

Cold storage plant apparatus. 

Cooking utensils. 

Dairy and milk handling machinery. 

Dyeing, bleaching and finishing machinery. 

Exterior building trim. 

Ham boilers. 

Household electrical appliances. 

Ice cream freezers and cabinets. 

Laundry machinery. 

Washing machines and parts. 

Meat slicing machine parts. 
Packing house equipment. 
Paper and pulp machinery. 
Electric refrigerator parts. 
Restaurant equipment. 
Salt dryer>. 

Soap making machinery. 
Soda fountains and counters 


Street lamps. 

Sugar refinerj machinery. 

Enduro A A 

Abattoir equipment. 
Bakery equipment. 
Bottling machinery. 

Builders' hardware. 

( andy making machinery. 

Canning or preserving equipment 
Chemical plant apparatus. 
( looking utensils. 
( iolf club heads. 

Ice making machinery. 

Nitric acid planl equipment. 

Nitrogen fixation apparatus 

Oil refinery equipment. 

Pyrometer protection tubes. 


Rubber plant machinery. 

Septic tanks. 

Scientific apparatus. 

Soot blowers. 

Tanks — all kinds. 

Varnish ket ties. 

Etc., etc. 

Enduro S 

Automobile parts such as pump shafts, etc 
Heater bars for paper mills. 
Gage and indicator parts. 

Locomotive safety valve seats. 

Mining i chiner^ and equipment. 
Hitle and revolver barrels. 

Pumps or pump parts. 
Railroad equipment . 
Steam turbine parts. 

Shafts for deep well pumps. 

Valve parts for high pressure steam, and 
oil refinery equipment. 

Parts requiring high phvsical proper! ies. 



Knduro is available in bars, castings, forcings, plates, sheets, strip, tubing, *ire and 

innumerable finished products through fabricators. 




Printed in I . S. \.